define([], () => {
    class Show {
        constructor() {
            this.box = document.querySelector('#bigbox')
    

            // console.log(this.box)
            this.showheader()
        
        }

        showheader() {
            window.onscroll = () => {
                let  scrollTop = document.documentElement.scrollTop || document.body.scrollTop
                if (scrollTop >= 100) {


                    //className 可以给一个标记设置类名
                    this.box.className = 'fx'
                    // this.box.className='box4'
                } else {

                    this.box.className = ''
                }
            }


        }
      
 







    }
    new Show()
})
   